Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Staphylococcus aureus isolate, WBG1022, was resistant to penicillin, kanamycin, neomycin, streptomycin, chloramphenicol, trimethoprim, cadmium, and ethidium bromide and harbored plasmids of 34.5, 24.5, 4.4, 3.2, and 2.6 kilobases. The plasmids were transferred in mixed-culture transfer and conjugation experiments. No resistance phenotype was associated with the 2.6-kb plasmid. The 3.2-kb and 4.4-kb plasmids encoded chloramphenicol and streptomycin resistance respectively. The 24.5-kb plasmid, pWBG626, encoded joint resistance to penicillin, kanamycin, neomycin, and ethidium bromide. Resistance to trimethoprim and cadmium were chromosomal. The 34.5-kb plasmid, pWBG661, had no resistance phenotype but was found to be conjugative. It also mobilized the 4.4-kb and 24.5-kb plasmids in WBG1022. Restriction endonuclease analysis of pWBG661 with EcoRI, ClaI, PvuII, and BglII restriction enzymes demonstrated that pWBG661 was identical to two previously isolated S. aureus conjugative plasmids, pWBG620 and pWBG637, that also lack resistance phenotypes.
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PMID:Transfer of plasmid-borne resistance from a multiply-resistant Staphylococcus aureus isolate, WBG1022. 760 89

Streptomycin resistance was detected in 17 of 20 multiply-resistant Staphylococcus aureus isolates from a hospital in a southeastern Nigerian town. The isolates were uniformly sensitive to methicillin, erythromycin, gentamicin, mupirocin, ciprofloxacin and vancomycin but produced beta-lactamase and were resistant to other antimicrobial agents and harbored different plasmids which ranged in size and number from 1.0 to c, 40 kb and one to six respectively. Curing and transfer experiments demonstrated that streptomycin resistance (Smr) was located on plasmids in 15 of the 17 isolates. 16 Smr plasmids were isolated and characterized. They belonged to three distinct groups based on size and resistance phenotypes. Eight 4.4 kb plasmids encoded Smr only, three 4.7 kb plasmids encoded resistance to streptomycin and chloramphenicol (SmCm) and five 23.8 kb plasmids encoded resistance to streptomycin, kanamycin, neomycin, cadmium and beta-lactamase production (CPKNS). Restriction endonuclease analysis demonstrated that the 4.4 kb Smr plasmids were similar to one another and indistinguishable from pUB109, an incompatibility group 5 Smr plasmid, suggesting that they may also belong to incompatibility group 5. The SmCm and the CPKNS plasmid groups also gave identical restriction patterns with single and double enzyme digests. Further transfer experiments with one of the SmCm plasmids led to the isolation of a 4.4 kb Smr plasmid which was indistinguishable from the other 4.4 kb plasmids, suggesting that the SmCm plasmids are natural recombinants between a streptomycin and chloramphenicol resistance plasmid. The results demonstrate a multiple origin of streptomycin resistance in the S. aureus population studied.
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PMID:Genetics of streptomycin resistance in methicillin-sensitive multiply-resistant Staphylococcus aureus. 762 50

Isolated nuclei from mammalian cells contain a calcium-dependent endonuclease. The produced DNA fragmentation is a necessary step in the sequence of events resulting in apoptosis (programmed cell death). We report here that zinc and cadmium inhibit the calcium-dependent endonuclease. The essential metal ion zinc may counterbalance the calcium-mediated apoptosis. In contrast to zinc, cadmium alone stimulates the endonuclease by replacing calcium. Thus cadmium exerts a dual effect: micromolar concentrations inhibit the apoptotic endonuclease in the presence but activate the enzyme in the absence of calcium.
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PMID:Effects of zinc and cadmium on apoptotic DNA fragmentation in isolated bovine liver nuclei. 784 11

DNA fragmentation in isolated rat liver nuclei is a Mg(2+)-dependent, multi-step process which is potentiated by Ca2+ and cleaves the DNA into > or = 700, 200-300 and 30-50 kilobase pair (kbp) fragments, prior to internucleosomal cleavage by Ca2+/Mg(2+)-dependent endonuclease(s). We now show that Cd2+, Hg2+, dichloroisocoumarin (DCI, a serine protease inhibitor) and N-ethylmaleimide (NEM) block both Mg2+ and Ca2+/Mg(2+)-dependent processes. Inhibition of DNA cleavage produced an increase in the size of the DNA fragments, from mono-/oligonucleosomes to 30-50, 200-300, > or = 700 kbp and finally to intact DNA. NEM and DCI inhibition was blocked by dithiothreitol, and it is proposed that a critical thiol(s) is involved in the DNA cleavage reactions which are a feature of the apoptotic process.
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PMID:Multi-step DNA cleavage in rat liver nuclei is inhibited by thiol reactive agents. 784 12

Isolated nuclei from mammalian cells contain a Ca(2+)-dependent endonuclease [1]. The produced DNA fragmentation is a necessary step in the sequence of events resulting in apoptosis [2]. We report here that zinc inhibits the DNA fragmentation in dependence of the free Ca2+ concentrations, suggesting that a balance between zinc and calcium might regulate the Ca(2+)-dependent endonuclease. Incubation of nuclei with different free calcium concentrations combined with cadmium shows a stronger inhibition of the DNA fragmentation than zinc. Cadmium inhibits the endonuclease in a calcium-independent way. Surprisingly cadmium alone is able to stimulate the endonuclease, thus to replace Ca2+.
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PMID:Cadmium and zinc mediated changes of the Ca(2+)-dependent endonuclease in apoptosis. 843 10

PI-SceI is an intein-encoded protein that belongs to the LAGLIDADG family of homing endonucleases. According to the crystal structure and mutational studies, this endonuclease consists of two domains, one responsible for protein splicing, the other for DNA cleavage, and both presumably for DNA binding. To define the DNA binding site of PI-SceI, photocross-linking was used to identify amino acid residues in contact with DNA. Sixty-three double-stranded oligodeoxynucleotides comprising the minimal recognition sequence and containing single 5-iodopyrimidine substitutions in almost all positions of the recognition sequence were synthesized and irradiated in the presence of PI-SceI with a helium/cadmium laser (325 nm). The best cross-linking yield (approximately 30%) was obtained with an oligodeoxynucleotide with a 5-iododeoxyuridine at position +9 in the bottom strand. The subsequent analysis showed that cross-linking had occurred with amino acid His-333, 6 amino acids after the second LAGLIDADG motif. With the H333A variant of PI-SceI or in the presence of excess unmodified oligodeoxynucleotide, no cross-linking was observed, indicating the specificity of the cross-linking reaction. Chemical modification of His residues in PI-SceI by diethylpyrocarbonate leads to a substantial reduction in the binding and cleavage activity of PI-SceI. This inactivation can be suppressed by substrate binding. This result further supports the finding that at least one His residue is in close contact to the DNA. Based on these and published results, conclusions are drawn regarding the DNA binding site of PI-SceI.
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PMID:Photocross-linking of the homing endonuclease PI-SceI to its recognition sequence. 1018 9

A target sequence-specific DNA binding region of the restriction endonuclease Sso II was identified by photocross-linking with an oligodeoxynucleotide duplex which was substituted with 5-iododeoxy-uridine (5-IdU) at the central position of the Sso II recognition site (CCNGG). For this purpose the Sso II-DNA complex was irradiated with a helium/cadmium laser (325 nm). The cross-linking yield obtained was approximately 50%. In the presence of excess unmodified oligodeoxynucleotide or with oligode-oxynucleotides substituted with 5-IdU elsewhere, no cross-linking was observed, indicating the specificity of the cross-linking reaction. The cross-linked Sso II-oligodeoxynucleotide complex was digested with chymotrypsin, a cross-linked peptide-oligodeoxy-nucleotide complex isolated and the site of cross-linking identified by Edman sequencing to be Trp61. In line with this identification is the finding that the W61A variant cannot be cross-linked with the IdU-substituted oligodeoxynucleotide, shows a decrease in affinity towards DNA and is inactive in cleavage. It is concluded that the region around Trp61 is involved in specific binding of Sso II to its DNA substrate.
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PMID:Identification of a base-specific contact between the restriction endonuclease SsoII and its recognition sequence by photocross-linking. 1066 47

Eleven Staphylococcus aureus plasmids encoding penicillinase production and resistance to different antibacterial agents were transferred to laboratory recipient strains in mixed-culture transfer and transduction experiments and characterized by restriction endonuclease analysis and incompatibility. The plasmids were differentiated into four types (types A-D) on the basis of their resistance phenotypes and restriction endonuclease patterns. One type encoded resistance to cadmium and arsenate. The second type encoded resistance to cadmium, mercuric compounds and nucleic acid-binding compounds. The third type encoded resistance to cadmium, kanamycin, neomycin and streptomycin while the fourth type encoded resistance to kanamycin, neomycin and ethidium bromide. Plasmids within the same class were structurally related or similar and were different from those in the other classes. Three plasmids, pWBG626, pWBG628, and pWBG663, representing three of the four plasmid types, belonged to incompatibility group 1. These new plasmids add to the number of known incompatibility group 1 plasmids and have resistance phenotypes which should be useful for studying incompatibility of new S. aureus plasmids.
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PMID:New Staphylococcus aureus incompatibility group 1 plasmids encoding penicillinase production and resistance to different antibacterial agents. 1123 98

Cell death resulting from cadmium (Cd) intoxication has been confirmed to occur through apoptosis by morphological and biochemical studies. However it is still not clear whether Cd itself or metallothionein (MT) induced by Cd is the major factor responsible for the apoptosis. Although apoptosis is inducible by exposure of cells to various stimuli, the common pathway involved is generally accepted to be activation of endonucleases that induce internucleosomal cleavage of DNA, resulting in the 'ladder' formation observed upon agarose gel electrophoresis and the chromatin condensation seen by electron microscopy. Cd does not seem to activate the endonuclease in vitro. However, Cd itself can be associated with apoptosis through indirect oxidative stress by inhibition of antioxidant enzymes and possible interaction with zinc finger protein. In addition to the direct effect of Cd, MT appears to play dual roles in apoptosis induction: one as a Cd carrier by which Cd accumulates in the nucleus, and the other as an inhibitor of zinc finger proteins, which include transcriptional factors related to apoptosis such as the product of the apoptosis resistance gene A20. In this review, we demonstrated that the mode of cell death following Cd exposure is associated with intracellular movement of Cd and MT. A possible mechanism for Cd-induced apoptosis is also discussed.
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PMID:Apoptosis induced by cadmium. 1464 32

Many environmental metals are co-carcinogens, eliciting their effects via inhibition of DNA repair. Apurinic/apyrimidinic (AP) endonuclease 1 (Ape1) is the major mammalian abasic endonuclease and initiates repair of this cytotoxic/mutagenic lesion by incising the DNA backbone via a Mg(2+)-dependent reaction. In this study we examined the effects of arsenite [As(III)], cadmium [Cd(II)], cobalt [Co(II)], iron [Fe(II)], nickel [Ni(II)], and lead [Pb(II)] at concentrations ranging from 0.3 to 100 microM on the incision activity of Ape1 in the presence of 1 mM MgCl(subscript)2(/subscript). Pb(II) and Fe(II) inhibited Ape1 activity at each of the concentrations tested, with an IC(subscript)50(/subscript) (half-maximal inhibitory concentration) of 0.61 and 1.0 microM, respectively. Cd(II) also inhibited Ape1 activity but only at concentrations > 10 microM. No inhibition was seen with As(III), Co(II), or Ni(II). A similar inhibition pattern was observed with the homologous Escherichia coli protein, exonuclease III, but no inhibition was seen with the structurally distinct AP endonuclease E. coli endonuclease IV, indicating a targeted effect of Pb(II), Fe(II), and Cd(II) on the Ape1-like repair enzymes. Excess nonspecific DNA did not abrogate the metal inactivation, suggesting a protein-specific effect. Notably, Cd(II), Fe(II), and Pb(II) [but not As(III), Co(II), or Ni(II)] inhibited AP endonuclease activity in whole-cell extracts but had no significant effect on single nucleotide gap filling, 5'-flap endonuclease, and nick ligation activities, supporting the idea of selective inactivation of Ape1 in cells. Our results are the first to identify a potential DNA repair enzyme target for lead and suggest a means by which these prevalent environmental metals may elicit their deleterious effects.
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PMID:Inhibition of Ape1 nuclease activity by lead, iron, and cadmium. 1515 9


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